These are photographs made with our homemade Juillan's
H-alpha coronograph in order to observe
Venus's atmosphère durin the egress.
The photographs were taken with a modified VestaPro webcam (RAW mode
with B&W sensor).
The phenomenom is the egress of the planet, at the end of the transit
(after 3rd contact)

Observation
of the egress with the coronograph, from 3rd contact...
Median stack from 5 selected raw images.
Note that Venus is still visible after 4th contact.

One
can remark that Venus luminosity is similar to the prominences's one
(about 1/100000 the sunlight),
that gives a magnitude of about -13.5! (to compare with the -3.5 magnitude
some days before the transit)

From
P.Tanga paper, an explanation about the polar point could be:
The deviation angle W caused by the atmposheric refraction effect
(and that deviates the light beam from the Sun to the observer)
varries with the latitude on Venus.
The observations showing a complete limb when the planet is close
from the solar limb and showing a polar point when the planet moves
away from the solar limb suggests values of W close from 43"
for low and intermediate latitudes et close from 90" for polar
zones.
In fact, as Venus always faces the Sun with the same hemisphere,
a climatic differentiation of the atmosphere could be probable.

Here
we composited 9 images among the last taken (at 11h38TU), where a
little part of the limb is still visible close from the South Pole.
By adding a grid corresponding to this time one can measure the angular
distance between the last limb of Venus observed and the closest solar
limb. If we approximate W to this angle we measure an angle about
88" for the polar zone.

Here,
we had observed variations in intensity on the limb, so we median-stacked
some images at the beginning of the egress: le bright limb is
well concentrated around the South Pole, but also we observe a
little brith spot on the right (green arrow), perhaps witnessing
variations in the refraction angle depending on the clouds heights
or absorptions...
First image is rotated and enlarged pixel-to-pixel;
Second image in enlarged with spline interpolation.

Here
again, some minutes after the previous image we clearly see two
bright spots: the one close from the pole and the other slightly
on the right (green arrow the West).
The two images have two different visualisation cuts.

In
order to illustrate the existence of the two spots, here is the
time evolution of the limb.
On this image we see the two persisting spots on the pole and on
the west of the pole (spoted by the two white dotted lines).
The image have the original orientation in order to avoid degradations
due to interpolated rotation.

Peu avant,
dans l'attente du troisième contact, on est passé en mode
coronographe et en décalant de disque on a pu suivre le phénomène
de sortie filtré en H alpha.While waiting the 3rd contact, we prepared
the coronograph but by shifting the image in order to observe the beginning
of the egress in H-alpha.